The purpose of the Center for Research in Reproductive Physiology is to continue to investigate, using systematic physiological and contemporary cellular and molecular approaches, the control systems that govern major reproductive processes in mammals, with a special emphasis on higher primates. The Center, which has grown and diversified over the last 5 years of support, is currently comprised of 18 research projects subserved to varying degrees by 4 research core facilities: Primate (Core B), Assay (Core C), Histology (Core D) and Molecular Endocrinology (Core E). The Molecular Endocrinology Core, which was recently established by intramural funds, is now formally proposed for the first time. The research interests of the Center are wide ranging, extending, for example, from studies of the molecular mechanisms regulating steroid receptor action at the genomic level to investigation of the neuroendocrine control system governing gonadal function at the organismic level. Because of the established relevance to the human situation of data obtained from non-human primates, a major emphasis of the Center's research activity is focused on the analysis of reproductive control systems in the monkey. In this regard, the neuroendocrine regulation of testicular and ovarian function, the endocrine and paracrine regulation of ovarian and testicular function, the neurobiological basis of puberty, the impact of nutritional and metabolic parameters on the hypothalamic-pituitary-gonadal axis, the neural basis of the GnRH pulse generator, and the endocrine and neurochemical bases of sexual behavior are being systematically studied using the rhesus and cynomolgus monkey as experimental models. Several clinical studies of reproduction in men and women are also subserved by the Center. Significant areas of endeavor utilizing non-primate paradigms include studies of the regulation of gonadotropin subunit gene expression by gonadal steroids and peptides, the neurobiological basis of the inhibition of the GnRH pulse generator induced by suckling, the neuroendocrine control of the timing of the onset of puberty, and the anatomy of the neurocircuitry controlling hypothalamic releasing factor secretion. The Center is also committed to providing advanced training at the postdoctoral level in the physiological analysis of reproduction, integrating molecular, cellular and systems approaches. There is every reason to believe that this concentrated research approach to the study of reproductive physiology, in concert with a greatly expanded training program, will continue to have direct impact on the treatment of reproductive disorders in man.